Optical switches are known and are useful in implementing optical communications networks using fiberoptic transmission lines. In such networks, it is at times necessary to switch the optical signals between optical transmission paths.
One known type of optical switch is an optical cross-connect switch. In such switches, in a general case, any one of N input lines can be coupled to any one of N output lines.
One known type of cross-connect switch 10 is implementable using the Spanke architecture illustrated in FIG. 1. In a Spanke architecture with N inputs and N outputs, N 1×N switches 12a, b, c, . . . n are connected by an interconnect fabric 16 to N 1×N output switches 18a, b . . . n.
The interconnect fabric 16 has N2 total static connections. One connection is between each input-output pair of switches. Therefore, an N×N fabric has a total of N2 fibers with N2 inputs and N2 outputs.
Insertion loss is a major concern in optical cross-connect switches. Although a single stage Spanke design can achieve small insertion loss, this solution creates yet another problem: namely, the difficulty of creating the large interconnecting fabric because the fabric contains N2 connections.
Methods are known to implement small interconnect fabrics. For example, pre-routed fibers can be sandwiched between flexible plastic sheets sometimes called optical flypapers. They are however very difficult to create for N>32. Alternately, the interconnections can be made from N2 individual fibers. However, this solution is time consuming to build and difficult to maintain.
There thus continues to be a need to be able to cost effectively design and implement larger cross connect switches of various sizes. It would be especially advantageous if it would not be necessary to custom create a different interconnect networks for each switch. Preferably, a known interconnect design can be reliably and cost effectively manufactured and could be used to implement a variety of switches.